Very fine Swiss 18k gold lever chronograph watch Circa 1921

Gold chronograph with instantaneous 30 min register by Longines
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A very fine Swiss 18 carat gold open faced chronograph keyless lever pocket watch with instantaneous 30 minute register, circa 1921. Made in one example only, sold to the headquarters of the Bern Police on August 9th, 1921. Frosted gilt movement, 19 jewels, straight-line lever escapement, anibal brass Guillaume balance with gold adjusting screws, blued steel Breguet balance spring with overcoil, Wilmot’s patent micrometer cam regulator. Gold hinged gold cuvette with engraved dedication. White enamel dial with bold painted Breguet numerals, outer minute and fifths of a second chronograph divisions, Arabic five minute/seconds numerals, subsidiary dials for the seconds and instantaneous 30 minute register, original blued steel Breguet hands. Matte case, cast and chased with the arms of Bern in high relief and the inscription Feuer Wehr Bern, chased foliate and floral bezels and band, foliate cast bow. Dial and movement signed. Accompanied by a letter from Longines confirming the date of sale and that only one example was made.
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Diameter: 51.5 mm
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Signed: Longines